1. Field of the Invention
This invention relates to clock-controlled digital signal devices arranged in a multiplexed CMOS system. More particularly, this invention relates to such a system where the outputs of clocked digital signal sources are supplied to a clocked multiplexer to produce a composite output merging the stream of both signal sources.
2. Description of the Prior Art
It is known in digital integrated circuit chips to split a data handling system into two data paths (odd and even) each running at one-half the basic data rate, and thereafter to merge the odd and even output signals to obtain the desired combined output signals. Such split data paths require more IC area, but since each data path runs at one-half the basic speed, the data handling elements are easier to design and to make than for devices running at full speed.
This split-path interleaved arrangement requires a multiplexer to combine the output signals from both data paths. Conventionally, the multiplexer is clocked by the same stream of clock pulses as are applied to the initiating data signal sources. This has turned out not to be an efficient arrangement, and further improvement is needed.
In a preferred embodiment of the invention, to be described hereinbelow in detail, first and second clocked digital sources are provided in each of two data paths respectively, and are clocked by respective direct and complementary clock pulses. The clocked outputs of these devices are directed to a multiplexer where the interleaved data path signals are recombined into a single output line. This multiplexer includes the usual clocked transmission gates, but in this invention the clock signals are shifted in time by 90xc2x0 from the clock signals applied to the originating signal sources. The result is that additional time is made available for sampling the digital signals applied to the multiplexer. Other objects, aspects and advantages of the invention will in part be pointed out in, and in part apparent from, the following description of a preferred embodiment, considered together with the accompanying drawings.